Balance Sheets Details - Accrued Liabilities (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Components of accrued liabilities
Payable in connection with construction in progress	$ 7,249,000	$ 4,135,000
Accrued compensation and related charges	3,707,000	4,774,000
Preferred stock dividends payable	2,901,000	2,901,000
Accrued professional services	868,000	930,000
Accrued product warranty	703,000	669,000	$ 743,000
Other tax payable	493,000	867,000
Current portion of operating lease liabilities	458,000	485,000
Advances from customers	305,000	338,000
Other personnel-related costs	286,000	291,000
Accrual for sales returns	39,000	112,000
Accrued income taxes		729,000
Other accrued liabilities	2,010,000	1,933,000
Accrued liabilities, Total	$ 19,019,000	$ 18,164,000